In the related art, in a turbine section of a gas turbine, an exhaust gas diffuser of a duplex tube structure connected to a combustion gas outlet of the turbine is used in order to recover the static pressure of a combustion gas from the turbine. However, in general, a gas turbine exhaust section including the exhaust gas diffuser is also an object to be cooled.
Usually, the gas turbine exhaust section is generally configured to include an exhaust gas diffuser having an outer diffuser and an Inner diffuser; an exhaust cavity having a casing wall and a bearing case provided so as to cover this exhaust gas diffuser; struts that couple the casing wall and the bearing case through the exhaust gas diffuser; and strut covers that couple the outer diffuser and the inner diffuser so as to cover the struts.
In such a gas turbine, for example, a cooling structure adapted to promote substitution of air within each strut or an exhaust tunnel, using a cooling system, and to enhance the cooling effect of the gas turbine exhaust section is disclosed in PTL 1.
PTL 1 describes a structure including the cooling system in which an air intake port that allows an exhaust tunnel communicating with an exhaust cavity through an exhaust gas diffuser on a downstream side of the exhaust cavity to communicate with a casing exterior is provided inside the exhaust gas diffuser, and air introduced from this air intake port is emitted from a space between the strut and the strut cover to the outside of the exhaust cavity through a pipe as suction exhaust means.